Mrs.Tess Chow, your mom can apply in chinese embassy in manila for 3 months visa. She need submit the following documents to the visa office of the embassy:
1/ Passport/travel document with blank pages and a validity of at least 6 months.
2/ One completed hong Kong Visa Application Form affixed with one passport-sized photo.
3/ One copy of the sponsor's HK ID and the sponsor's telephone number;
4/ Proofs of relationship between applicant and sponsor.
5/ an invitation letter in which the sponsor agrees to provide financial support and accommodation
Because the visa application is required to be first approved by Immigration Department of Hong Kong, so the embassy needs one month to process the visa.